diff --git a/test-requirements.txt b/test-requirements.txt
index 2415bcb..afd4651 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,4 +1,4 @@
-hacking>=0.12.0,!=0.13.0,<0.14
+hacking>=3.0,<4.0.0 # Apache-2.0
 
 coverage>=3.6
 fixtures>=1.3.1
diff --git a/tox.ini b/tox.ini
index afc320e..b2453f9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,7 +35,9 @@ commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenote
 # H405 multi line docstring summary not separated with an empty line
 ## TODO(ruhe) following checks should be fixed
 # E721 do not compare types, use 'isinstance()'
+# W503 line break before binary operator
+# W504 line break after binary operator
 show-source = True
-ignore = E721,H404,H405,H803
+ignore = E721,H404,H405,H803,W503,W504
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
diff --git a/yaql/__init__.py b/yaql/__init__.py
index eddd54f..9d8cf93 100644
--- a/yaql/__init__.py
+++ b/yaql/__init__.py
@@ -49,6 +49,7 @@ def detect_version():
     except pkg_resources.DistributionNotFound:
         return 'Undefined (package was not installed with setuptools)'
 
+
 __version__ = detect_version()
 
 
@@ -117,6 +118,7 @@ def create_context(data=utils.NO_VALUE, context=None, system=True,
 
     return context
 
+
 YaqlFactory = factory.YaqlFactory
 
 
diff --git a/yaql/language/contexts.py b/yaql/language/contexts.py
index b61bccc..f412594 100644
--- a/yaql/language/contexts.py
+++ b/yaql/language/contexts.py
@@ -78,7 +78,7 @@ class ContextBase(object):
         while p is not None:
             context_predicate = None
             if predicate:
-                context_predicate = lambda fd: predicate(fd, p)
+                context_predicate = lambda fd: predicate(fd, p)  # noqa: E731
             layer_overloads, is_exclusive = p.get_functions(
                 name, context_predicate, use_convention)
             p = None if is_exclusive else p.parent
@@ -137,7 +137,7 @@ class Context(ContextBase):
         if use_convention and self._convention is not None:
             name = self._convention.convert_function_name(name)
         if predicate is None:
-            predicate = lambda x: True
+            predicate = lambda x: True  # noqa: E731
         return (
             set(six.moves.filter(predicate, self._functions.get(name, set()))),
             name in self._exclusive_funcs
diff --git a/yaql/language/parser.py b/yaql/language/parser.py
index a6302b5..d7dfb1a 100644
--- a/yaql/language/parser.py
+++ b/yaql/language/parser.py
@@ -33,9 +33,9 @@ class Parser(object):
         for up, bp, op_name, op_alias in yaql_operators.operators.values():
             self._aliases[op_name] = op_alias
             if up:
-                l = precedence_dict.setdefault(
+                la = precedence_dict.setdefault(
                     (abs(up), 'l' if up > 0 else 'r'), [])
-                l.append('UNARY_' + op_name if bp else op_name)
+                la.append('UNARY_' + op_name if bp else op_name)
                 unary_doc += ('value : ' if not unary_doc else '\n| ')
                 spec_prefix = '{0} value' if up > 0 else 'value {0}'
                 if bp:
@@ -44,14 +44,14 @@ class Parser(object):
                 else:
                     unary_doc += spec_prefix.format(op_name)
             if bp:
-                l = precedence_dict.setdefault(
+                la = precedence_dict.setdefault(
                     (abs(bp), 'l' if bp > 0 else 'r'), [])
                 if op_name == 'INDEXER':
-                    l.extend(('LIST', 'INDEXER'))
+                    la.extend(('LIST', 'INDEXER'))
                 elif op_name == 'MAP':
-                    l.append('MAP')
+                    la.append('MAP')
                 else:
-                    l.append(op_name)
+                    la.append(op_name)
                     binary_doc += ((
                         'value : ' if not binary_doc else '\n| ') +
                         'value {0} value'.format(op_name))
@@ -81,7 +81,7 @@ class Parser(object):
                 value = precedence_dict.get((i, oa))
                 if value:
                     precedence.append(
-                        (('left',) if oa is 'l' else ('right',)) +
+                        (('left',) if oa == 'l' else ('right',)) +
                         tuple(value)
                     )
         precedence.insert(0, ('left', ','))
diff --git a/yaql/language/runner.py b/yaql/language/runner.py
index 74cb4a6..6324543 100644
--- a/yaql/language/runner.py
+++ b/yaql/language/runner.py
@@ -12,6 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+# flake8: noqa: E731
+
 import sys
 
 import six
@@ -107,7 +109,7 @@ def choose_overload(name, candidates, engine, receiver, context, args, kwargs):
     if len(candidates2) == 0:
         raise_not_found()
 
-    arg_evaluator = lambda i, arg: (
+    arg_evaluator = lambda i, arg: (  # noqa: E731
         arg(utils.NO_VALUE, context, engine)
         if (i not in lazy_params and isinstance(arg, expressions.Expression)
             and not isinstance(arg, expressions.Constant))
diff --git a/yaql/language/utils.py b/yaql/language/utils.py
index c4be672..d761216 100644
--- a/yaql/language/utils.py
+++ b/yaql/language/utils.py
@@ -28,6 +28,7 @@ def create_marker(msg):
             return msg
     return MarkerClass()
 
+
 KEYWORD_REGEX = re.compile(lexer.Lexer.t_KEYWORD_STRING.__doc__.strip())
 NO_VALUE = create_marker('<NoValue>')
 
@@ -51,6 +52,7 @@ def is_mutable(obj):
                             collections.MutableSet,
                             collections.MutableMapping))
 
+
 SequenceType = collections.Sequence
 MutableSequenceType = collections.MutableSequence
 SetType = collections.Set
diff --git a/yaql/language/yaqltypes.py b/yaql/language/yaqltypes.py
index c276957..13e0e7a 100644
--- a/yaql/language/yaqltypes.py
+++ b/yaql/language/yaqltypes.py
@@ -140,7 +140,7 @@ class MappingRule(LazyParameterType, SmartType):
                 *args, **kwargs):
         super(MappingRule, self).convert(
             value, receiver, context, function_spec, engine, *args, **kwargs)
-        wrap = lambda func: lambda: func(receiver, context, engine)
+        wrap = lambda func: lambda: func(receiver, context, engine)  # noqa
 
         return utils.MappingRule(wrap(value.source), wrap(value.destination))
 
diff --git a/yaql/standard_library/queries.py b/yaql/standard_library/queries.py
index 4df2966..f96a6ae 100644
--- a/yaql/standard_library/queries.py
+++ b/yaql/standard_library/queries.py
@@ -359,7 +359,7 @@ def all_(collection, predicate=None):
         true
     """
     if predicate is None:
-        predicate = lambda x: bool(x)
+        predicate = lambda x: bool(x)  # noqa: E731
 
     for t in collection:
         if not predicate(t):
@@ -1529,10 +1529,10 @@ def merge_with(engine, to_list, d, another, list_merger=None,
         {"a": 1, "c": [2, 3], "b": 3, "d": 5}
     """
     if list_merger is None:
-        list_merger = lambda lst1, lst2: to_list(
+        list_merger = lambda lst1, lst2: to_list(  # noqa: E731
             distinct(engine, lst1 + lst2))
     if item_merger is None:
-        item_merger = lambda x, y: y
+        item_merger = lambda x, y: y  # noqa: E731
     return _merge_dicts(d, another, list_merger, item_merger, max_levels)
 
 
diff --git a/yaql/tests/test_collections.py b/yaql/tests/test_collections.py
index 24771ff..8b2e400 100644
--- a/yaql/tests/test_collections.py
+++ b/yaql/tests/test_collections.py
@@ -48,7 +48,8 @@ class TestCollections(yaql.tests.TestCase):
         self.assertTrue(self.eval('isList($.keys().toList())', data=data))
 
     def test_list_concatenates_and_flatten_generators(self):
-        generator_func = lambda: (i for _ in range(2) for i in range(3))
+        generator_func = lambda: (i for _ in range(2)   # noqa: E731
+                                  for i in range(3))
 
         self.context['$seq1'] = generator_func()
         self.context['$seq2'] = generator_func()
diff --git a/yaql/tests/test_queries.py b/yaql/tests/test_queries.py
index bc2cbab..fb2d953 100644
--- a/yaql/tests/test_queries.py
+++ b/yaql/tests/test_queries.py
@@ -115,7 +115,7 @@ class TestQueries(yaql.tests.TestCase):
         self.assertEqual(100, self.eval('[].sum(100)'))
 
     def test_memorize(self):
-        generator_func = lambda: (i for i in range(3))
+        generator_func = lambda: (i for i in range(3))  # noqa: E731
         self.assertRaises(
             TypeError,
             self.eval, '$.len() + $.sum()', data=generator_func())
diff --git a/yaql/tests/test_system.py b/yaql/tests/test_system.py
index a7a0224..370535e 100644
--- a/yaql/tests/test_system.py
+++ b/yaql/tests/test_system.py
@@ -70,7 +70,7 @@ class TestSystem(yaql.tests.TestCase):
             self.eval('[2].select($ + 1).assert(len($) = 1).first()'))
 
     def test_lambda_passing(self):
-        delegate = lambda x: x ** 2
+        delegate = lambda x: x ** 2  # noqa: E731
         self.assertEqual(
             9,
             self.eval('$(3)', data=delegate))
@@ -91,7 +91,7 @@ class TestSystem(yaql.tests.TestCase):
             self.eval('$func(5, z => 2, y => 1)', data=func))
 
     def test_lambda_expression(self):
-        delegate = lambda x: x ** 2
+        delegate = lambda x: x ** 2  # noqa: E731
         self.assertEqual(
             9,
             self.eval('$.x[0](3)', data={'x': [delegate]}))
@@ -101,19 +101,19 @@ class TestSystem(yaql.tests.TestCase):
             self.eval('($.x[0])(3)', data={'x': [delegate]}))
 
     def test_2nd_order_lambda(self):
-        delegate = lambda y: lambda x: x ** y
+        delegate = lambda y: lambda x: x ** y  # noqa: E731
         self.assertEqual(
             16,
             self.eval('$(2)(4)', data=delegate))
 
     def test_2nd_order_lambda_expression(self):
-        delegate = lambda y: {'key': lambda x: x ** y}
+        delegate = lambda y: {'key': lambda x: x ** y}  # noqa: E731
         self.assertEqual(
             16,
             self.eval('$(2)[key](4)', data=delegate))
 
     def test_2nd_order_lambda_collection_expression(self):
-        delegate = lambda y: lambda x: y ** x
+        delegate = lambda y: lambda x: y ** x  # noqa: E731
         self.assertEqual(
             [1, 8, 27],
             self.eval(